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Gas Exchange in Plants
What are the two main
gases that all
organisms on earth
need to exchange
back and forth
between themselves
and the environment?
OXYGEN AND CARBON
DIOXIDE
Why do autotrophs and heterotrophs
need to exchange these gases?
A. Autotrophs
SUCH AS . . .
1. Need CO2 for
photosynthesis.
2. Use O2 for cellular
respiration.
3. Get rid of excess O2 through . . .
STAY TUNED!
Why do autotrophs and heterotrophs
need to exchange these gases?
B. Heterotrophs
SUCH AS . . .
1. Use O2 for cellular
respiration.
2. Get rid of CO2 as a
waste gas.
How do flowering plants exchange
these gases?
They use three
vegetative
structures:
1. Roots
2. Stems
3. Leaves
How do flowering plants exchange
these gases?
1. Roots
a. CO2 dissolves in water
in soil.
b. CO2 absorbed by root
hairs; transported by
xylem
c. Photosynthesis produces O2;
transported by phloem.
How do flowering plants exchange
these gases?
2. Stems
a. Lenticels – tiny
(white “spots” are the
openings in stems for
openings)
gas exchange.
How do flowering plants exchange
these gases?
3. Leaves
a. Review leaf’s cross-section structure.
Cuticle
Upper epidermis
Palisade layer
Spongy layer
Lower
epidermis
Guard cells and
stomata
How do flowering plants exchange
these gases?
3. Leaves
b. O2 and CO2 AND H2O
are exchanged at
stomata formed by
guard cells.
c. Guard cells are in OPEN
position when filled with
water and CLOSED when
water is scarce.
Guard cell Animation
How do flowering plants exchange
these gases?
3. Leaves
d. What type of plant
would be most likely
found in the
rainforest? One with
lots of guard cells or
one with few guard
cells?
LOTS OF GUARD CELLS –
WHY?
How do flowering plants exchange
these gases?
3. Leaves
e. Gas exchange also
happens at spongy
layer and palisade
layer.